Catheter-based temporary radiation therapy following balloon angioplasty has been shown in clinical studies to reduce restenosis. This program is concerned with developing a permanently implanted radioactive stent which can also reduce restenosis. In Phase I, Implant Sciences demonstrated that a coronary stent could be ion implanted with radioactivity accurately and uniformly and without any wash-off of radioactivity from the stent surface. Also a special radioactive ion source was designed for an existing ion implanter which could safely handle the radioactive source material. In Phase II we plan to answer some perplexing questions raised by some European clinical studies which have shown more restenosis beyond each end of the radioactive stent than within the stent boundaries. This will be done using a porcine animal model. These studies will also compare a low energy x-ray emitter 103Pd with the beta emitter 32P using the same target dose at the adventia of the coronary artery. The animal study, to be done at the Washington Hospital Center will evaluate the degree of restenosis and late lumen loss at 1,3, and 6 month intervals both within and beyond the stent boundaries. PROPOSED COMMERCIAL APPLICATIONS: This research could lead to the high volume ion implantation of coronary stents with radioactive isotopes. Radioactive stents have been shown to markedly reduce restenosis after angioplasty. Implant Sciences Corporation plans to offer the ion implantation as a service to stent manufacturers.